Cartridge fuse holder and indicator with eccentrically mounted contact



Jan. 11, 1966 E. BORYS 3,

CARTRIDGE FUSE HOLDER AND INDICATOR WITH ECCENTRICALLY MOUNTED CONTACT Filed July 17, 1962 26 mvamoa IzmZ 50/395 United States Patent 3,229 665 CARTRIDGE FUSE HOLDER AND TNDTCATSR WITH ECCENTRTCALLY MQUNTED CQNTAT Emil Borys, 710 Old Rand Road, Lake Zurich, Ill. Filed July 17, 1962, Ser. No. 210,318 2 Claims. (Cl. 2ll0130) This invention relates to a new and useful screw plug type cartridge fuse holder and indicator adapted to be screwed or otherwise rotata ly engaged into a socket such as a fuse socket or lamp-type socket. This is a continuation-in-part application of my application filed November 13, 1959, Serial No. 852,914, now United States Patent 3,047,695.

The fuse holder and indicator of this invention serves a number of purposes. It serves to hold and support a cartridge-type fuse so that when the holder is screwed into a socket, such as a fuse socket, the holder serves the same purpose as an ordinary screw plug type of fuse. Also, the subject of this invention serves as an indicator to indicate when the cartridge-type fuse has been blown. This is accomplished by providing the fuse holder with a small neon bulb and appropriate electrical connections to indicate the blown condition of the cartridge-type fuse. The cartridge-type fuse may be readily removed when blown or when it is desired to replace it with a different type of fuse. Thus, the fuse holder and indicator of the present invention is a permanent item, the life of which is only dependent on the life of the neon bulb which is good for many thousands of hours of operation. Since the neon bulb glows or is in operation only when the fuse is blown, it will be seen that the holder and indicator has an indefinite life for practical purposes.

Fuse holders of the type described above contain a central axially extending well for the reception of the cartridge-type fuse. A detachable setscrew contact is threaded into the inner end of the fuse holder, and this contact engages one end terminal of the cartridge-type fuse, holding the same in place in the fuse holder. Whenever an overload condition occurs, blowing the cartridgetype fuse, the setscrew contact may become fused to the central contact in the socket which receives the fuse holder. Accordingly, when the fuse holder is unscrewed from the socket after this condition occurs for replacement of the cartridge-type fuse, the small set-screw contact remains in the socket. This separation of the setscrew contact from the fuse holder occurs even if a threaded connection is used between it and the fuse holder, since rotation of the holder during its removal merely results in unscrewing the setscrew contact from its seat in the inner end of the fuse holder. Whenever this small setscrew contact becomes fused to the socket, a long shut-down period is required before this contact can be removed. This results in long delays and inefficient operation of the system of which the fuse is a component part. Quite often the setscrew contact itself is damaged during its removal from the socket necessitating replacement of this part or the discarding of the entire cartridge fuse holder. Also, this fusing of the contact creates a hazardous condition for those responsible for correcting the situation.

Accordingly, it is a principal object of this invention to provide a cartridge fuse holder and indicator having means for insuring a positive separation of the setscrew contact from the fuse holder socket during removal of the fuse holder after an overload condition has occurred.

Another object of this invention is the provision of a screw plug type cartridge fuse holder and indicator of the kind described which is foolproof, versatile in use, and formed of mass produced, low-cost components which may be readily assembled.

3,229,065 Patented Jan. 11, 1966 These and other objects and advantages of the invention will become apparent from the following specification wherein like numerals refer to similar parts throughout.

In the drawings:

FIG. 1 is a top plan view of a screw plug type cartridge fuse holder and indicator forming one embodiment of this invention;

FTG. 2 is a section taken along a line 2-2 of FIG. 1 with certain parts being shown in elevation; and

FIG. 3 is a circuit diagram illustrating the operation of the fuse holder and indicator of this invention.

Briefly, and by way of introduction, positive separation of the fuse holder setscrew contact from the socket contact is accomplished by eccentrically locating the setscrew contact with respect to the central axis of the body of the fuse holder. In this way, rotary movement of the fuse holder during its removal necessarily results in a circular path of travel for the entire setscrew contact shearing the same from the socket contact.

Referring especially to FIGS. 1 and 2, the screw plug type cartridge fuse holder and indicator of this invention, generally designated 1, includes a cylindrical plug body 2 having a closed outer end 3 and an open inner end 4. integrally extending from the inside surface of the closed end 3 is a baffle 5 which defines in the plug body 2 a well 6 for the reception of a cartridge-type fuse 7. The baffle 5 also defines a second well 8 adapted to contain the indicator of the fuse holder of this invention which will be described in greater detail below. Because of the offcenter location of the baffle 5, both wells are eccentric with respect to a central axis of the plug body.

A screw shell 9 formed of copper, brass, or other electrically conductive material and having an inwardly eX- tending annular flange 10 is press fitted over the inner end of the plug body 2 with the annular flange 10 serving to secure a washer 11 in place over the open end of the plug body 2. The washer 11, which is formed of insulating material, contains an eccentrically located aperture in which is secured a female support 12. The female support 12 in the form of an internally threaded sleeve is made of copper, brass or other like conducting material and this member serves as a receptacle for a setscrew contact 13 which is cross-slotted in a known manner.

A spring detent type of terminal 14 is disposed on the inside of the outer end 3 of the plug body so as to be coaxial with the cartridge fuse 7 and contact 13. It will be apparent that the cartridge fuse 7 is securely retained within the fuse holder and indicator with the opposite terminals thereof being engaged by the setscrew contact 13 and the terminal 14, respectively. Upon removal of the contact 13, the cartridge fuse 7 may be readily removed and replaced within a few seconds.

A conductor 15, which is preferably formed of the same piece of spring tempered conducting metal as the terminal 14, interconnects the latter member with the screw shell contact 9. This conductor extends through a small notch 16 in the wall of the plug body 2 for engagement with the screw shell contact 9.

A miniature neon bulb 17 is disposed in the well 8 of the plug body 2 with its tip extending just slightly through a small window 18 provided in the face of the closed end 3. These miniature neon bulbs are well known and are commercially available in quantity. When a sufficient difference in potential or voltage is impressed across the grids or electrodes the neon or other gas on the interior of the envelope will be ionized and glow.

One of the terminals of the bulb 17 is electrically connected to the female support 12 by a conductor 19. The other terminal of the bulb 17 is connected to the screw 3 shell contact 9 by a conductor 20 which is attached to the conductor by a soldered connection 21'.

It may be desirable to place a resistor 22 in a series circuit relationship in the conductor 19. These miniature resistors 22 may be obtained commercially at any desired rating, such as between 50,000 and 250,000 ohms. If the cartridge fuse holder and indicator 1 is to be used in circuits where the voltage does not exceed 24 volts, for example, it will usually be unnecessary to provide a resistor 22. The use of a miniature neon bulb 17 of a type that will have a long life at such voltages is all that is required. On the other hand, if the cartridge fuse holder and indicator is to be used in circuits where the voltage is, say 115 or 220 volts, then it will usually be more economical to insert a miniature resistor 22 of the proper rating in the conductor 19 thereby protecting the neon bulb and obtaining the full life thereof.

It will be seen that all of the components of the fuse holder and indicator of this invention may be mass produced at low cost. In fact, such a component as the screw shell contact 9, the female support 12, the contact 13, the neon bulb 17, the resistor 22 and the cartridge fuse 7 are standard components or items which can be procured on the open market. Therefore, the body 2 and the washer 11 are the only special parts, and these parts may be readily manufactured with little expense as by injection molding in multiple-cavity molds from a suitable plastic such as polystyrene, phenolformaldehyde, etc.

Referring to FIG. 3, a source of alternating current, such as 115 volts, is indicated at 25 with a pair of conductors 26 and 27 leading therefrom to a load diagrammatically indicated at 28. The cartridge fuse holder and indicator 1 of FIGS. 1 and 2 is indicated in circuit relationship in conductor 27. That is, the cartridge fuse is indicated at 7 and the neon bulb indicated at 17. As long as the fuse 7 is not blown, it provides a shunt or short across the neon bulb 17 so that no potential is impressed across the grids or electrodes within the gas filled envelope. Hence, the bulb does not glow. However, if the cartridge fuse 7 blows or fails for any other reason, a potential Will be impressed on one of the grids and the gas Within the bulb will be ionized and glow with the ions draining off to the ground through an opposite grid electrode. The glowing of the neon bulb 17 then tells one that the cartridge fuse 7 has blown and that the same requires replacement.

As mentioned above, when an overload condition occurs in the circuit blowing the cartridge-type fuse, the set-screw contact of the fuse holder may become fused to the contact which is part of the socket that receives the fuse holder. In other Words, the exposed end of the contact 13 becomes adhered to the contact in the fuse holder socket. In the fuse holder of this invention the contact 13 is eccentrically mounted with respect to a central axis extending through the cylindrical plug body 2. Accordingly, when the plug body 2 is rotated for removal of the same from its socket, the contact 13 itself will rotate in a circular path about the central axis of the cylindrical plug body. This movement provides a shearing force producing a clean separation between the exposed end of the contact 13 and the contact in the fuse holder socket. It should be realized that it is not necessary to provide a threadable connection between the female support member 12 and the setscrew contact 13. A simple frictional engagement between the two members is satisfactory. Because of the eccentric mounting of the contact 13, there is no tendency for it to remain in the fuse holder socket upon removal of the fuse holder from the same.

Thus it will be seen that by this invention a fuse holder and indicator has been provided which will ensure a positive separation of the setscrew contact from the fuse holder socket during removal of the fuse holder after an overload condition has occurred. The device is inexpensive to manufacture and is quite durable in operation.

While the invention has been shown in but one form it will be obvious to those skilled in the art that it is not so limited, but rather it is susceptible of various changes and modifications without departing from the spirit and scope of the appended claims.

What is claimed as new is:

1. A screw plug-type cartridge fuse holder comprising, a generally cylindrical hollow plug body formed of insulating material and having one end thereof closed, a screw shell contact secured on the other end of said body, means at said other end of said body for substantially closing the same, a cylindrical contact supported by said means with the longitudinal central axis of the contact in eccentric relation with the longitudinal central axis of said body, a fuse in said body in axially extending relation therewith, said contact having the inner end thereof in engagement with one end of said fuse for holding the latter in said body and said contact having the outer end thereof exposed for engagement with a conducting member in a fuse holder socket, the outer end of said contact being substantially circular and in concentric relation with the longitudinal central axis of the contact, whereby said contact is caused to orbit upon rotation of said body about its longitudinal central axis.

2. A screw plug-type cartridge fuse holder comprising, a generally cylindrical hollow plug body formed of insulating material and having one end thereof closed, a screw shell contact secured to the other end of the body and having an inwardly extending annular flange, an insulating washer secured over the other end of said body by said annular flange, which washer has an opening therein with the central axis of the opening in eccentric relation with the longitudinal central axis of said body, a fuse axially disposed in said body in alignment with said opening, an internally threaded sleeve fitted in said opening, and a cylindrical contact threadingly secured in said sleeve, which contact has the inner end thereof in engagement with one end of said fuse for holding the latter in said body and which contact has the outer end thereof exposed for engagement with a conducting member in a fuse holder socket, the outer end of said contact being substantially circular and in concentric relation with the longitudinal central axis of the contact, whereby said contact is caused to orbit upon rotation of said body about its longitudinal central axis.

References Cited by the Examiner UNITED STATES PATENTS 816,406 3/1906 Weber et al. 200 1,952,460 3/1934 Rittenhouse 200-119 1,957,345 5/1934 Kriegstedt 200121 2,074,917 3/1937 Kauffman 200--121 2,186,920 1/ 1940 Currie 200119 3,047,695 7/ 1962 Borys 200-121 BERNARD A. GILHEANY, Primary Examiner, 

1. A SCREW PLUG-TYPE CARTIDGE FUSE HOLDER COMPRISING, A GENERALLY CYLINDRICAL HOLLOW PLUG BODY FORMED OF INSULATING MATERIAL AND HAVING ON END THEREOF CLOSED, A SCREW SHELL CONTACT SECURED ON THE OTHER END OF SAID BODY, MEANS AT SAID OTHER END OF SAID BODY FOR SUBSTANTIALLY CLOSING THE SAME, A CYLINDRICAL CONTACT SUPPORTED BY SAID MEANS WITH THE LONGITUDINAL CENTRAL AXIA OF THE CONTACT IN ECCENTRIC RELATION WITH THE LONGITUDINAL CENTRAL AXIS OF SAID BODY, A FUSE IN SAID BODY IN AXIALLY EXTENDING RELATION THEREWITH, SAID CONTACT HAVING THE INNER END THEREOF IN ENGAGEMENT WITH ONE END OF SAID FUSE FOR HOLDING THE LATTER IN SAID BODY AND SAID CONTACT HAVING THE OUTER END THEREOF EXPOSED FOR ENGAGEMENT WITH A CONDUCTING MEMBER IN A FUSE HOLDER SOCKET, THE OUTER END OF SAID CONTACT BEING SUBSTANTIALLY CIRCULAR AND IN CONCENTRIC RELATION WITH THE LONGITUDINAL CENTRAL AXIS OF THE CONTACT, WHEREBY SAID CONTACT IS CAUSED TO ORBIT UPON ROTATION OF SAID BODY ABOUT ITS LONGITUDINAL CENTRAL AXIS. 